Partial wafermap process is a process where a single silicon wafer is cut into two or more pieces for the reason of smaller lot quantity. The wafers are usually halved or quartered. Before the implementation of inkless wafer processing, an ink dot placed on a die by a prober in a wafer fab identifies a bad die. No ink dot on the die represents a good die. When the inked wafer is sent over to an assembly and test site, the wafer could be halved or quartered to accommodate smaller lot quantity. This is when the term “partial lot” is used. Any part of the halved or quartered wafer (normally termed as H1, H2 for halved wafer, and Q1, Q2, Q3, Q4 for quartered wafer) could be processed on any die mounting machine without requiring any relationship between the partial wafers.
A wafermap (or inkless system) eliminates the inking process at the prober in the wafer-fab. Replacing the ink for marking the bad dies from the good ones, a map file is created for each of the probed wafer that indicate the location of good and bad dies based on known position termed as reference die. When one particular wafer is halved or quartered, one half or one quarter of the wafer has a reference die. There is a need for a new reference die for each of the partial wafers.
Prior art methods are described in U.S. Pat. No. 6,216,055 of Balamurugan et al. Entitled “Partial Semiconductor wafer processing” and U.S. Pat. No. 6,174,788 of Balamurugan entitled “Partial Semiconductor Wafer Processing With Multiple Cuts of Random Sizes.” These patent are incorporated herein by reference. The prior art teaches a method of providing a locator die teach by the production operator on die mounting machine (pick and place equipment).
The current process does the following steps:                1. Lot started        2. Send wafer to partial production operator (PO).        3. PO will record wafer identification, and quarter or half wafer using saw machine.        4. Q1 for first quarter or H1 for first half will be issued to the line, and Q2, Q3, Q4 or H2 will be kept in the die bank.        5. Die mounting machine PO will do a locator die teach on the die mounting machine.        
In step 4 above, the die exact quantity of the partial wafer is not known. Due to this, a quantity estimate will have to be done by the partial operator. This will cause quantity discrepancies at the die bonder causing yield losses and other lot processing problems.
In step 5 above is the step that needs to be taken by the machine operator in order to reach the locator die position for each H1 or Q1 wafer so that the locator die coordinate is recorded for the subsequent processing of Q2, Q3, Q4 or H2 or H2 parts.
FIG. 1 illustrates the flow of partial map process at the die bonder in the prior art. The steps are:                1. Load partial wafer to die bonder.        2. Download wafermap data for whole wafer.        3. Display the whole wafer in die bonder monitor.        4. Move the wafer table to first die pickup position.        5. Move display cursor to first die pickup position.        6. Teach two limit dies in X direction.        7. Teach two limit dies in the Y direction.        8. Using limit die coordinates information remove other partial wafer dies from map.        9. Start die mount.        
The above process also requires dependencies of the system on all die bonder machine operators. Any error made in this process will prevent further processing of H2 or Q2, Q3 or Q4 part due to lack of locator die.
The current method is error prone, and is limited. It is highly desirable to provide a method where there is no need for teaching of the locator die at the die mounting machine.